Improvement of trochanteric bone quality in an osteoporosis model after short-term treatment with parathyroid hormone: a new mechanical test for trochanteric region of rat femur

We have examined the changes induced in the trochanteric region of femur of ovariectomized rat after administration of estradiol and p.arathyroid hormone. We have developed a reproducible biomechanical test and produced trochanteric fractures to evaluate stiffness and strength of this region in addition to histomorphometry. We investigated the short-term effects of parathyroid hormone (PTH) and estrogen (E) on the strength of the rat trochanteric region in a new mechanical test. Forty-four 3-month-old female Sprague-Dawley rats were ovariectomized and 8 weeks later treated with soy-free diet (C), daily applications of orally supplied E (0.5 mg/kg food) or subcutaneously injected PTH (0.014 mg/kg), for 5 weeks, and an additional untreated group was added as sham-operated. The femurs were examined for biomechanical and histomorphometric changes. Our new mechanical test was validated in a right-left comparison. The PTH treatment induced significantly superior biomechanical results (F (max) = 225.3 N, stiffness = 314.9 N/mm) compared to E (F (max) = 182.9 N, stiffness = 237.2 N/mm), C (F (max) = 166.03 N, stiffness = 235.56 N/mm), and sham (F (max) = 192.1 N, stiffness = 267.2 N/mm). Animals of the PTH group demonstrated a significantly improved trabecular bone structure and area (75.67%) in comparison to the E (61.04%) and C (57.18%) groups. Our new biomechanical test is valid and produces trochanteric fracture. Our results show that the short-term antiosteoporotic effects of PTH are in the trochanteric region of ovariectomized rat superior to E.